text: The equations in the previous subsection reveal that the , , and  terms originate through three distinct mechanisms. 
  The  term arises from Zeeman splitting of the ground or excited degenerate states. These field-dependent changes in energies of the magnetic sublevels causes small shifts in the bands to higher/lower energy. The slight offsets result in incomplete cancellation of the positive and negative features, giving a net derivative shape in the spectrum. This intensity mechanism is generally independent of sample temperature.
  The  term is due to the field-induced mixing of states. Energetic proximity of a third state  to either the ground state  or excited state  gives appreciable Zeeman coupling in the presence of an applied external field. As the strength of the magnetic field increases, the amount of mixing increases to give growth of an absorption band shape. Like the  term, the  term is generally temperature independent. Temperature dependence of  term intensity can sometimes be observed when  is particularly low-lying in energy. 
  The  term requires the degeneracy of the ground state, often encountered for paramagnetic samples. This happens due to a change in the Boltzmann population of the magnetic sublevels, which is dependent on the degree of field-induced splitting of the sublevel energies and on the sample temperature. Decrease of the temperature and increase of the magnetic field increases the  term intensity until it reaches the maximum (saturation limit). Experimentally, the  term spectrum can be obtained from MCD raw data by subtraction of MCD spectra measured in the same applied magnetic field at different temperatures, while  and  terms can be distinguished via their different band shapes.
  The relative contributions of A, B and C terms to the MCD spectrum are proportional to the inverse line width, energy splitting, and temperature:
  where  is line width and  is the zero-field state separation. For typical values of  = 1000 cm,  = 10,000 cm and  = 6 cm (at 10 K), the three terms make relative contributions 1:0.1:150. So, at low temperature the  term dominates over  and  for paramagnetic samples.